1. Field of the Invention
The present invention relates to a damper of a drum type washing machine, and more particularly, to a damper of a drum type washing machine capable of attenuating vibration transmitted to a tub at the time of a washing operation.
2. Description of the Conventional Art
FIG. 1 is a longitudinal section view of a drum type washing machine in accordance with the conventional art.
As shown, the conventional drum type washing machine 10 comprises a cabinet 11 for forming an appearance; a tub 12 arranged in the cabinet 11 for storing washing water; a drum 13 rotatably arranged in the tub 12 for performing a washing operation and a dehydrating operation for laundry; and a driving motor 14 positioned at a rear side o the tub 12 and connected to a rotation shaft 13a of the drum 13.
A door 15 through which laundry is put in or taken out is rotatably arranged at a front surface of the cabinet 11, and a bracket 16 for supporting the rotation shaft 13a of the drum 13 is arranged at a rear surface of the tub 12.
A spring 17 is fixed to the cabinet 11 at an upper portion of the tub 12, and a damper 20 for attenuating vibration transmitted to the tub 12 by the drum 13 is arranged at a lower portion of the tub 12.
FIG. 2 is a longitudinal section view showing the damper of the drum type washing machine in accordance with the conventional art.
As shown, the conventional damper 20 comprises a cylinder 21 fixed to the cabinet 11 and having an accommodating portion 21a; a rod 22 fixed to the tub 12 and arranged to be inserted/detachable into/from the accommodating portion 21a of the cylinder 21; and a damping 23 coupled to an outer circumferential surface of the rod 22 and contacting a frictional surface 21b of the cylinder 21.
Operation of the conventional damper will be explained as follows.
At the time of a washing operation, force is applied to the rod 22 downwardly due to vibration transmitted to the tub by the drum. At this time, the damping 23 comes into contact with the frictional surface 21b of the cylinder 21 thus to generate a frictional force. According to this, the rod 22 gradually moves thus to attenuate vibration transmitted to the tub 12.
In order to attenuate vibration transmitted to the tub 12, the damping 23 has to be designed by sufficiently considering a frictional force thereof. However, in the damper of the conventional drum type washing machine, vibration widths generated at the time of a normal dehydration operation and an excessive dehydration operation under a substantial washing operation are greatly different to each other, thereby having a limitation in efficiently attenuating both vibrations of a great width and a less width.
In the conventional damper of the drum type washing machine, a frictional force of the damping is constantly maintained at all times, so that both vibrations of a great width and a less width are not efficiently attenuated. Also, when a frictional force of the damping is excessively great or less, noise is generated and a lifespan of the drum type washing machine is reduced.